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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
9700 BIOLOGY
9700/04
Paper 4 (Theory 2), maximum raw mark 60
This mark scheme is published as an aid to teachers and students, to indicate the requirements of the
examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began.
All Examiners are instructed that alternative correct answers and unexpected approaches in
candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills
demonstrated.
Mark schemes must be read in conjunction with the question papers and the report on the
examination.
The grade thresholds for various grades are published in the report on the examination for most
IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses.
•
CIE will not enter into discussions or correspondence in connection with these mark schemes.
CIE is publishing the mark schemes for the October/November 2006 question papers for most IGCSE,
GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level
syllabuses.
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.c
MARK SCHEME for the October/November 2006 question paper
s
er
GCE Advanced Subsidiary Level and GCE Advanced Level
Page 2
Question
1
(a)
1
2
3
4
5
(b)
(c)
Mark Scheme
GCE A/AS LEVEL - OCT/NOV 2006
Syllabus
9700
Paper
4
Expected Answers
Marks
(carbohydrates)
less reduced / less hydrogen / less C-H bonds ;
R H2
for, aerobic respiration / ETC / NAD / ATP ;
less energy ;
per, unit mass / mole ;
accept figs for 3 and 4
carbohydrate has lower energy density ;; accept as alternative to 3 & 4 for 2 marks
3 max
carbohydrate = 1.0 ;
lipid = 0.6 – 0.8 ;
2
RQ remains stable between 3°C and 10°C / AW ;
rise between 10°C and, 20°C / 25°C ;
0.74 to, 0.76 / 0.8 ;
sharp rise, between 25°C and 27°C / after 25°C ;
0.8 to 0.91 / peaks at 0.91 ;
accept difference for figs marks
3 max
at low temperatures hamster uses lipids ;
reason ; e.g. more heat generated from lipid respiration
at higher temperatures more carbohydrates are used ;
(d)
4 max
anaerobic respiration / conversion of carbohydrate to fats as animal hibernates;
[Total: 10]
© UCLES 2006
1
Page 3
Question
2
Mark Scheme
GCE A/AS LEVEL - OCT/NOV 2006
Syllabus
9700
Paper
4
Expected Answers
(a) (i)
(ii)
(iii)
black
1
:
black
2
:
red
3
Marks
red ;
1 ;
copper
1
:
2
red ;
1 ;
2
copper ;
1
;
2
(b) (i)
(ii)
test / back, cross ;
with, copper / AtAt / homozygous recessive ;
if all offspring red, homozygous ;
if some offspring copper, heterozygous ;
ref. equal proportions of offspring ;
mark (i) and (ii) together
[Total: 10]
© UCLES 2006
4 max
Page 4
Question
3
Paper
4
Marks
control / maintain, water / solute, concentration / potential ;
of, body fluids / internal environment / cells ;
1
2
3
4
5
6
7
8
9
10
(c)
Syllabus
9700
Expected Answers
(a)
(b)
Mark Scheme
GCE A/AS LEVEL - OCT/NOV 2006
2
B / C, lower ψ than A ;
accept C lower ψ than B
accept ψ gets more negative as fluid moves down descending limb
comparative figs ;
water moves out by, diffusion / osmosis ;
into, medulla tissue / tissue fluid ;
D / E, higher ψ than C ;
accept ψ gets less negative as fluid moves up ascending limb
comparative figs ;
Na+ / Cl-, move out ;
into, medulla tissue / tissue fluid ;
by active transport ;
A and E same ψ / AW ;
penalise once for no units
allow either 4 or 8
receptor – hypothalamus ;
effector – pituitary gland / cells or walls of collecting duct ;
5 max
R anterior pituitary
[Total: 9]
© UCLES 2006
2
Page 5
Question
4
(a)
(b)
Mark Scheme
GCE A/AS LEVEL - OCT/NOV 2006
Syllabus
9700
Paper
4
Expected Answers
Marks
similar morphological, physiological, biochemical and behavioural features ;
(minimum 3 for mark )
interbreed / reproduce ;
produce fertile offspring ;
occupy same niche ;
reproductively isolated;
2 max
isolating mechanism – land barrier / AW ; accept geographical isolation
type of speciation – allopatric ;
2
(c)
1
2
3
4
5
6
7
8
geographical barriers / description ;
barrier to gene flow ;
no interbreeding / separate breeding populations / reproductively isolated ;
(gene) mutations occur / new alleles ;
different selection pressures / e.g. of selection pressure ;
ref. natural selection / description ;
change in allele frequency / OWTTE ;
develop different chromosome numbers / ref. polyploidy ;
4 max
[Total: 8]
© UCLES 2006
Page 6
Question
5
(c)
Syllabus
9700
Paper
4
Expected Answers
(a)
(b)
Mark Scheme
GCE A/AS LEVEL - OCT/NOV 2006
5.0 – 5.5 ;
µm ;
1
2
3
4
5
6
7
8
Marks
accept correct values for mm, cm or m
plant produces ABA ;
(due to) high temperature ;
(due to) reduced water supply / water loss / drought ;
guard cells lose K+ ;
ref. water potential gradient ;
guard cells lose water ;
loss of turgor causes stomatal closure ;
AVP ; e.g. stress hormone / different thickness of cell wall / ABA binds to receptors
on guard cells
2
4 max
(rate of transpiration due to) difference in relative humidity inside and outside,
stomata / leaf ;
in still air / low wind speed, external water vapour remains close to stomata / AW ;
reduced, concentration gradient / water potential gradient ;
2 max
[Total: 8]
© UCLES 2006
Page 7
6
(a)
(b)
Syllabus
9700
Paper
4
Describe how the structure of neurones speeds up the transmission of action
potentials.
(b)
(a)
Mark Scheme
GCE A/AS LEVEL - OCT/NOV 2006
[6]
Explain, using a named example, how sensory receptors in mammals convert
[9]
energy into action potentials.
[Total: 15]
1
2
3
4
5
6
7
8
9
10
11
myelin sheath / schwann cell ;
insulates, axon / dendron ;
impermeable to Na+ / K+ ;
depolarisation only at nodes of Ranvier ;
ref. local circuits ;
action potentials ‘jump’ from node to node ;
saltatory conduction ;
speed increased by 50 times / 0.5 ms-1 to 100 ms-1 ;
axons with large diameter / giant axon ;
reduce resistance ;
elongated, axon / dendron / neurone ;
12
13
14
15
16
17
18
19
20
21
22
23
24
ref. specific example ; e.g. pacinian corpuscle / rod / cone / hair cell
correct stimulus ; e.g. touch / pressure light / sound
detail of receptor response ; e.g. deformation of pacinian corpuscle membrane
stimulus causes Na+ channels to open ;
Na+ enters cell ;
K+ channels open ;
K+ leaves cell ;
depolarisation ;
receptor / generator potential ;
greater than threshold leads to, action potential / impulses ;
less than threshold only localised depolarisation ;
increased stimulus leads to increased frequency of action potentials ;
AVP ;
apply max 8 for points 15 - 24
9 max
6 max
Total 15
© UCLES 2006
Page 8
7
Mark Scheme
GCE A/AS LEVEL - OCT/NOV 2006
Syllabus
9700
(a)
Describe the transfer of energy to ATP during photosynthesis.
(b)
Describe the process of oxidative phosphorylation.
Paper
4
[6]
[9]
[Total: 15 ]
(a)
1
2
3
4
5
6
7
8
9
10
light absorbed by chlorophyll / AW ;
ref. photosystems ;
ref. harvesting clusters / accessory pigments ;
reaction centre / P680 / P700 ;
excitation of electrons / AW ;
ETC ;
idea of different energy levels ;
ADP + Pi → ATP ;
cyclic / non-cyclic, photophosphorylation ;
chemiosmosis / ATP synthase / description ;
11
12
13
14
15
16
17
18
19
20
21
22
23
reduced NAD / FAD ;
passed to ETC ;
hydrogens removed ;
R H2
split into H+ and e- ;
e- passed to carriers ;
H+ stays in mitochondrial matrix ;
oxygen final e- carrier ;
joins with H+ / reduced ;
R H2 / hydrogen
forms water ;
ref. energy levels of carriers ;
energy available to convert ADP and Pi to ATP ;
occurs three times ( for each reduced NAD ) / ref. total yield ;
chemiosmosis / ATP synthase / description ;
6 max
(b)
© UCLES 2006
9 max
[Total: 15]